Why is this useful? Well, If someone simply gets on your nerves, this feature allows you to screen out content from that person, and your forum experience might be improved as a result. Access to the posts of said persons is just a click away, in the event that you decide you DO want to see a particular post.
To use this feature, you must first login to the forums and then access your User Control Panel. Further information on how the process works can be found at the CHGPA Friends & Foes Tutorial, which provides a step-by-step guide for its use.
Notice the wording: This might improve your forum experience. Using this feature to filter content out is admittedly a very crude solution. Even people who you disagree with might provide posts that are valuable and on-topic. Heck, we don't want to follow the example of the US Congress, right?
But if a crude solution makes the difference between participating in the CHGPA forums vs. not participating at all.... Well then, you might want to give this a try. As I mentioned, you *can* still access the content that you have decided to block. If the posts from other pilots within a given topic spark your interest, all you have to do is click a link to see the entirety of the topic's content.